The objective of this project is to develop an intravascular optical imaging device that will aid in the diagnosis of atherosclerosis. According to statistics compiled by the American Heart Association, cardiovascular disease affects over 61 million Americans and is the leading cause of death in the United States. Atherosclerosis is indicated as a primary factor in three fourths of deaths resulting from cardiovascular disease. It is now recognized that the danger of atherosclerosis is not primarily due to narrowing of the arteries. Many coronary events and strokes are caused by atherosclerotic plaques that rupture. It is important that the cardiologist be able to assess the risk of plaque rupture when diagnosing and treating persons with atherosclerosis. The risk of plaque rupture is related to its structure and composition. Our spectral imaging technology is capable of resolving the small structural features important to identifying vulnerable plaques. Currently available imaging tools (angioscopy, MRI, intravascular ultrasound) do not provide the high spatial resolution needed for this application. An intravascular device based on our technology, which combines spatial imaging for structural detail and spectroscopic measurement for plaque composition, will provide important information for the cardiologist making risk assessments and choosing the best course of treatment.